The present invention relates to a brake system in which stroke of a brake operating means such as a brake pedal can be changed relative to the same braking effort.
In a brake system of an automobile, a master cylinder is actuated by pedaling a brake pedal so as to develop master cylinder pressure which is then supplied to wheel cylinders. The wheel cylinders thus develop braking forces, thereby braking the automobile. The brake system of this type is well known. In this case, the brake system employs a boosting device, which is operated by fluid pressure such as vacuum pressure, hydraulic pressure, or compressed air pressure, interposed between the brake pedal and the master cylinder. The boosting device is actuated by pedaling the brake pedal to boost leg-power exerted on the brake pedal to output boosted power for actuating the master cylinder, thereby providing large braking force with small leg-power on the brake pedal.
In such a brake system, the same pedal stroke results always the same braking force. That is, the braking force is determined relative to the pedal stroke without other choice.
However, as the same pedal stroke results always the same braking force, it can not keep up with the improvement of its responsiveness such as its operational feeling.
Therefore, a boosting device has been proposed in Japanese Patent Publication Showa 57-4547, which can keep up with the improvement of its responsiveness by changing the relation between the pedal stroke and the braking force. In the boosting device disclosed in this publication, a power piston is brought in contact with one side of one end of a power lever, an input rod is brought in contact with one side of the other end of the power lever, and an output rod is brought in contact with the other side of an intermediate portion of the power lever. In this manner, the displacement of the input rod becomes a value which is the displacement of the output rod subtracted by the displacement of the other end of the power lever by the rotation of the power lever, thereby obtaining larger displacement of the output rod even with a small displacement of the input rod. That is, the boosting device of the publication is designed to change the displacement of the output rod, i.e. the braking force, at a constant ratio relative to the displacement of the input rod.
However, since the aforementioned boosting device is designed to change the displacement of the output rod at a constant ratio relative to the displacement of the input rod, the displacement of the output rod can not be changed to any different value relative to the displacement of the input rod as long as using the boosting device. Further, since the displacement of the output rod is always changed relative to the displacement of the input rod in the aforementioned boosting device, the displacement of the output rod is changed even when the user wishes not to change the displacement of the output rod relative to the displacement of the input rod.
As mentioned above, as the displacement of the output rod is changed always and at a constant ratio relative to the displacement of the input rod, it is difficult to obtain good operational feeling and also difficult to set proper pedal stroke corresponding to vehicle condition such as load, brake operating condition, and/or a driver.
It is an object of the present invention to provide a brake system which allows the traveling range of a brake operating means to be controlled freely.
In order to achieve this object, a brake system of the present invention is a brake system in which a braking force output means produces braking forces corresponding to the braking operation of a brake operating means, and is characterized in that the traveling range of the brake operating means can be changed by fluid control.
Further, a brake system of the present invention comprises: a brake operating means; a brake pressure output means for producing brake fluid pressure according to the operation of the brake operating means; and a braking force output means for producing braking forces according to the brake pressure, and is characterized by further comprising a traveling range control means for allowing the traveling range of the brake operating means to be changed by fluid control, wherein the traveling range of the brake operating means is changed by the traveling range control means.
The present invention is characterized in that the brake pressure output means has a pressure boosting device, and the traveling range control means is provided in the pressure boosting device.
Further, the present invention is characterized in that the traveling range control means controls the relative displacement of an output member of the pressure boosting device relative to an input member of the pressure boosting device by using fluid to change the traveling range of the brake operating means.
Furthermore, the present invention is characterized in that the traveling range control means controls the reaction of a reaction mechanism of the pressure boosting device by using fluid to control the displacement of the output member relative to the input member.
Moreover, the present invention is characterized in that the traveling range control means controls the displacement of a control valve means of the brake boosting device relative to the output means by using fluid to control the displacement of the output member relative to the input member.
In addition, the present invention is characterized in that the brake pressure output means comprises a pressure boosting device and a master cylinder actuated by the pressure boosting device, and the traveling range control means is provided between the pressure boosting device and the master cylinder.
Further, the present invention is characterized in that the traveling range control means controls the displacement of a piston of the master cylinder relative to an output member of the pressure boosting device by using fluid to change the traveling range of the brake operating means.
Furthermore, the present invention is characterized in that the brake pressure output means has a master cylinder and the traveling range control means is provided in the master cylinder.
Moreover, the present invention is characterized in that the traveling range control means is provided between the brake pressure output means and the braking force output means.
In addition, the present invention is characterized by further comprising a fluid pressure source for producing fluid pressure, wherein the traveling range control means has a solenoid switching valve which selectively switches to supply either one of the fluid pressure from the brake pressure output means or the fluid pressure from the fluid pressure source to the braking force output means.
Further, the present invention is characterized in that the change of the traveling range of the brake operating means is conducted whenever predetermined condition is satisfied.
Furthermore, the present invention is characterized in that the predetermined condition is set based on at least one of conditions such as vehicle load condition, brake operating condition, road surface condition, and choice by a driver.
In the brake system of the present invention as structured above, the stroke of the brake operating means can be variously changed by using fluid at any time or whenever necessary. Since the stroke of the brake operating means can be changed by using fluid, the stroke can be variously set in a simple manner of controlling the fluid by the electronic control unit.
Therefore, the brake operating means can be set variously to have a proper pedal stroke corresponding to vehicle condition such as load, brake operating condition, and/or choice by a driver.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.